Spike (aka Puppy Fish) has been very ill. I posted about him a few days ago explaining his symptoms in the entry, "Suddenly Sick! Lump on side of my Betta!" I have tried everything.
-Epsom Salt bath a couple times
-water changes
-antibiotics
-fasting
-water testing
-covering the top of the bowl partially to retain for warmth and humidity
his symptoms have not changed. I think that he does have a tumor. Originally I thought it might be constipation or swim bladder. Now the new symptoms: color loss from his chin to his belly. I though it was brown fungus of some sort but I realize now that its the color fading. Also, he has now gone to the bottom of the bowl. He was hanging out on his leaf on top before. Close to the water heater. That is his favorite spot to hang and make bubble nests. Now today he is sitting on the rocks at the bottom and doesn't seem to be able to swim straight. He is a little bent over to one side and seems to float backwards if he tries to swim toward the surface. I am afraid he is going to drown down there! He is about 3 years old. Could these be signs of an aging and (I hate to say this) dying fish? Has anyone ever been through this before?? I will do everything that I can to make him more comfortable and well.

Housing
What size is your tank? 25 Gallons
What temperature is your tank? 76.5-79 degrees
Does your tank have a filter? yes
Does your tank have an air stone or other type of aeration? no
Is your tank heated? yes
What tank mates does your betta fish live with? none

Food
What type of food do you feed your betta fish? pellets, bloodworms
How often do you feed your betta fish? one or two pellets a couple times a day, bloodworms only special occasion treats

Maintenance
How often do you perform a water change? once a week. 25 to 50%. if needed occasional 90% (like after medication course)

What percentage of the water do you change when you perform a water change? 25 to 50%. if needed occasional 90% (like after medication course)

What type of additives do you add to the water when you perform a water change? water conditioner and a ph balancing additive if needed upon water test

Why does the tank swing so many degrees? I would invest in a better heater than can hold the temp. Those swings can be really hard on fish. You need like a good 100w+. I like Aqueon Pro myself, but Jager are good too and generally cheaper.

If your tank is cycled you shouldn't see nitrites. How long as the tank been set up and are you sure it's cycled? Also you should stop with the ph drops. PH swings can be lethal to bettas but they can adapt to a wide variety of PHs as long as it's somewhere like 6.8-8.6. 9+ then you're going to have to do something, but in that case I would suggest mixing RO in to soften it.

What medications have you used? If it's not a tumor, and it could be, he needs something that goes internal like Kanaplex or Maracyn Plus (not to be confused with Maracyn or Maracyn II)\

The epsom salts should be in 1/4 to 1 tsp per gallon and you can leave him in it for weeks.. I see you last posted only 2 days ago. Quick baths aren't going to do anything. You need to leave him in it for several days up to a week or two to see relief using epsom salts. I would re administer the epsom salts and leave him in them. If he can't get to the surface you may need to cup him and float the cup in the tank water so that he can stay warm. You'll need to mix the epsom salts into at least 1 gallon batches to keep the ratios right, and then make water changes out of the cup using the mixed up batch. You'll need to do at least a couple changes a day (like 1 in the am and one in the pm) because ammonia will build very quickly in those little cups. I've seen it get to be 4 ppm in 24 hours.. so watch it. That way also you can monitor his poop and see what it looks like. In the mean time I would not feed.